This invention relates to the underwater cutting and partial removal of a jet pump beam bolt retainer used in the pressure vessels of certain kinds of nuclear reactors for securing the jet pump beam of a jet pump assembly during initial reactor equipment assembly. These retainers interfere with the separate removal of the jet pump beam and beam bolt, that is without simultaneously removing other significant jet pump assembly parts.
Many kinds of nuclear reactors, in particular boiling water reactors, employ jet pumps to circulate cooling water or moderator fluid through the core within the pressure vessel of the reactor. During servicing outages of the reactor, it is on occasion desirable to remove and replace the jet pump beam and certain associated pieces of equipment without removing more pieces than is necessary. This may for example occur when cracking has been detected in the jet pump beam.
Information regarding the role of the jet pump beam in securing the upper portion of the jet pump assembly is provided in a below-referenced patent application to the assignee herein, General Electric Company. This patent application is entitled "Ultrasonic Method and Apparatus" and has a U.S. Patent and Trademark Office Ser. No. 220,431 and a filing date of Dec. 29, 1980 now U.S. Pat. No. 4,394,345. This application is hereby expressly referred to and incorporated herein.
A boiling water reactor may employ as many as twenty downwardly directed jet pumps to circulate reactor water through the core of the reactor pressure vessel. The jet pumps receive water from an inlet riser and pass the water through a pipe elbow or mixer to a jet pump nozzle, as shown for example in U.S. Pat. Nos. 3,378,456 and 3,389,055, both assigned to General Electric Company and incorporated herein. Each pipe elbow or mixer is held in position by a jet pump beam, which will be described in substantial detail hereinafter.